1. Field of the Invention
This invention relates to a semiconductor device package and, in particular, to a semiconductor device package for a semiconductor chip having a large number of electrodes.
2. Description of the Related Art
FIGS. 9 and 10 show an example of a semiconductor device on which a semiconductor chip having a large number of electrodes is mounted. Devices of this type have come to be used as the result of the recent trend toward high density semiconductor devices. In the semiconductor device shown, a semiconductor chip 1 is fixed within a rectangular recess 34 formed at the center of a package body 3. A first step section 31 is formed around the recess 34 of the package body 3 surrounding the recess 34. Formed around the first step section 31 is a second step section 32 which surrounds the first step section 31. A plurality of inner electrodes 51 and 52 are respectively formed on the first and second step sections 31 and 32, a plurality of electrodes 2 formed on the surface of the semiconductor chip 1 being connected to the inner electrodes 51 or 52 corresponding thereto through metal wires 41 or 42. Formed on the bottom surface of the package body 3 are a plurality of outer electrodes 6 which are respectively electrically connected to the corresponding inner electrodes 51 or 52.
In this semiconductor device, the inner electrodes 51 and 52 are arranged in a step-like manner with respect to each other, so that the pitch between adjacent inner electrodes 51 or 52 can be large notwithstanding the fact that the semiconductor chip 1 having a large number of electrodes is mounted thereon.
As shown in FIG. 10, however, while the distance l.sub.1 between the electrodes 2 of the semiconductor chip 1 and the inner electrodes 51 on the first step section 31, which is relatively near the semiconductor chip 1, can be short, the distance l.sub.2 between the electrodes 2 of the semiconductor chip 1 and the inner electrodes 52 on the second step section 32, which is spaced relatively far apart from the semiconductor chip 1, is inevitably large. Furthermore, if the number of electrodes of the semiconductor chip 1 is augmented and the inner electrodes are arranged in three steps or more, the distance between the outermost inner electrodes and the electrodes 2 of the semiconductor chip 1 must be made still larger. If, for example, the inner electrodes 51, 52 and 53 are, as shown in FIG. 11, arranged in three steps, i.e., on the first, second and third step sections 31, 32 and 33, the distance l.sub.3 between the electrodes 2 of the semiconductor chip 1 and the inner electrodes 53 on the third step section 33 must be made still larger.
Hence, if the distance between the inner electrodes 53 provided on the package body 3 and the electrodes 2 of the semiconductor chip 1 is large, the metal wires 43 connecting them to each other inevitably need to be quite long. As a result, there is the danger that some of these long metal wires 43 may hang downwards on account of their own tendency to curl or due to oscillations exerted on this semiconductor device, etc., and thus came into contact with inner electrodes 51 or 52 on the first or second step section 31 or 32 situated therebelow, as shown in FIG. 11. There is also the danger of adjacent metal wires 42 coming into contact with each other, as shown in FIG. 12. Consequently, the device is subject to electrical short-circuit accidents, which implies a certain reduction in the reliability of the semiconductor device.